class_docstr: A helper class that represents input string that to be modified.
  
  Text that Sample contains parsed in data set,
  ``TextField`` provides multiple methods for Sample to modify.
  
  Support sentence level and word level modification,
  default using word level API.
code: def text(self):
      if self._text or self._text == "":
          return self._text
      else:
          if self.split_by_space:
              self._text = " ".join(self.words)
          else:
              self._text = self.text_processor.inverse_tokenize(
                  self.words
              )
          return self._text
  
imports: from .field import Field
  from ....common.utils.list_op import *
  from ....common.preprocess.en_processor import EnProcessor
  from ....common.settings import ORIGIN, TASK_MASK, MODIFIED_MASK
label_desc: Use image node_id 21 for calling the TextField obj's underlying member method code with example usage: obj.text() and returns: self, self